Various techniques are used to introduce medicinal drugs into a patient's body, including injection and oral administration of medicine in solid or liquid form. Injection is an effective way to rapidly introduce medicine into a patient's bloodstream. However, patients often experience anxiety and discomfort from injections. Further, infection due to needle contamination is of growing and significant concern.
One type of conventional "needleless" drug injection system includes a mechanism, such as a plunger, by which a narrow stream of medicine is forced out of a nozzle at a very high speed to penetrate the patient's skin. Illustrative "needleless" injection systems are described in U.S. Pat. Nos. 5,599,302 (Lilley et al.), 5,383,851 (McKinnon et al.) and 5,064,413 (McKinnon et al.). While such apparatus prevents infection due to needle contamination, injection of the high speed stream can still cause discomfort and anxiety.
While oral administration of medicine is often preferable to injection, this technique suffers certain drawbacks. For example, in some circumstances, manufacture of a drug in a form suitable for oral administration degrades the effectiveness of the drug. Other drawbacks are related to the taste of a liquid medicine, the shape and/or size of a pill or tablet form, and stomach irritation.
Another technique for administering certain medicines is by absorption through the patient's skin (i.e., transdermally). Conventional transdermal drug delivery techniques include the use of ultrasonic energy or other forms of high-frequency energy. For example, in U.S. Pat. No. 5.421,816 (Lipkovker), ultrasound energy is used to move a drug through a patient's skin into the bloodstream. In U.S. Pat. No. 5,386,837 (Sterzer), pulse shocks of high-frequency energy, such as RF, microwave, infra-red or laser energy, are employed to create transient pores in the membranes of targeted diseased cells through which drug or chemotherapeutic agents can easily enter the targeted cells. U.S. Pat. No. 5,614,502 (Flotte et al.) describes the use of high pressure impulse transients, as may be created by laser-induced ablation, in combination with the administration of certain compounds. The high pressure, laser generated impulse works in combination with the therapeutic compound by generally increasing cell permeability in the region of impulse administration.
As used herein, the term "drug delivery" refers to the action by which a drug, medicament, compound, chemical agent, biological agent or the like (collectively, "agents") passes from the outside of cell(s) to the interior of cell(s) to effect a therapeutic, chemical or biological activity. Drug delivery includes transdermal drug delivery, the passage of drugs, compounds and the like through tissue including organs and cell cultures, both in vivo and in vitro. The term "biologic material" encompasses skin, organ tissue, cell cultures and the like.